Carbon dioxide capture from air leading to bis[N-(5-methyl-1H-pyrazol-3-yl-κN ²)carbamato-κO]copper(II) tetrahydrate

A mononuclear square-planar Cu II complex of (5-methyl-1 H -pyrazol-3-yl)carbamate, [Cu(C 5 H 6 N 3 O 2 ) 2 ]·4H 2 O, was synthesized using a one-pot reaction from 5-methyl-3-pyrazolamine and copper(II) acetate in water under ambient conditions. The adsorption of carbon dioxide from air was facilitated by the addition of diethanolamine to the reaction mixture. While diethanolamine is not a component of the final product, it plays a pivotal role in the reaction by creating an alkaline environment, thereby enabling the adsorption of atmospheric carbon dioxide. The central copper(II) atom is in an (N 2 O 2 ) square-planar coordination environment formed by two N atoms and two O atoms of two equivalent (5-methyl-1 H -pyrazol-3-yl)carbamate ligands. Additionally, there are co-crystallized water molecules within the crystal structure of this compound. These co-crystallized water molecules are linked to the Cu II mononuclear complex by O—H...O hydrogen bonds. According to Hirshfeld surface analysis, the most frequently observed weak intermolecular interactions are H...O/O...H (33.6%), H...C/C...H (11.3%) and H...N/N...H (9.0%) contacts.